Paracetamol, the common over-the-counter painkiller found in popular products like Panadol, may numb emotions as well as pain.

The potential side effect of deadened joy and pleasure was discovered for the first time in a recent US study published in the journal Psychological Science.

“Rather than just being a pain reliever, [paracetamol] can be seen as an all-purpose emotion reliever”, lead author Geoffrey Durso, a PhD student in psychology at The Ohio State University, said in a statement.

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Both positive and negative emotions are numbed by the drug, the results suggest.

Half of participants were given 1000mg of the drug, equal to two pills, with the other half given a placebo.

After waiting an hour for the drug to take effect, both groups were shown a series of pleasing and distressing photos, including crying children and children playing with kittens.

Those who had unknowingly taken the active drug reported weaker feelings across the emotional spectrum.

But the study involved a mere 82 participants, a relatively small sample size, suggesting the results should be treated cautiously.

The Ohio State University research team intends to test whether other common pain relievers ibuprofen and aspirin have a similar effect on emotions.